Rotary pumps have rotatable members including vanes for moving a fluid, such as air, through a compression chamber. These pumps have seal structures interposed between the movable and stationary parts to reduce leakage and enhance the compressors efficiency. The engaging parts of these rotary pumps are subject to high sliding speeds which may result in wear and considerable friction which limit the efficiency and useful life of the pumps. Examples of rotary piston compressors are shown in Lawton in U.S. Pat. Nos. 2,423,507 and Jerneas in 3,221,664.